Absorption of carotenoids is a complex process involving release from the food microstructure matrix, dissolution into mixed micelles, intestinal uptake, incorporation into chylomicrons, distribution to the tissues, uptake by liver and re-secretion into VLDL, which are progressively transformed into LDL.
Lycopene absorption from food sources is widely documented. Lycopene bioavailability is quite low from foods such as tomatoes and tomato juice. Up to now, tomato paste is the best known food source for bioavailable lycopene. Tomato contains about >90% of lycopene in its all E configuration.
Tomato extracts containing a high amount of lycopene are commercially available in the form of oleoresin but the bioavailability of the carotenoid in humans is rather limited from these sources. In concentrated tomato extracts, lycopene is mainly present in crystalline form, which has been suggested to be one of the primary factors that reduces its bioavailability.
To date, most commercially available lycopene sources display an isomeric profile quite similar to the starting tomatoes or show only a slight increase in Z-isomers, whether they are derivatives (such as sauces) or extracts. A number of treatments, as for instance thermal processing, are known to promote isomerization. Shi et al., Journal of Food Process Engineering 2003, 25, 485-498, showed that an increase in Z isomers could be obtained by heating tomato sauces. However certain lycopene isomers are not stable and prone to retro-isomerization. According to the literature, 5-Z is the most stable among the predominant lycopene isomers followed by the all-E, the 9-Z and the 13-Z. Accordingly, the stability of isomerized lycopene based products depends on their lycopene isomer profile and thus can be modulated by technological processing affecting this profile.
Thermal isomerization of lycopene is known to improve its bioavailability from food matrices. However, the bioavailability of individual lycopene isomers has not been investigated yet. As for stability, it can be assumed that bioavailability of lycopene based products is dependent on their lycopene isomer profile and thereby can be modulated by technological means.
There are already patents that propose technological means and formulations for improved bioavailability of carotenoids. For example, WO 2005/075575 provides a primary composition enriched in Z-isomers, effective to increase the bioavailability of the carotenoid compound. However, there is still a need for a carotenoid-containing product that has higher stability and thus increased bioavailability.